There is no such thing as a 1.44MB standard format floppy disc.

The term 1.44Mb floppy disc is a bastard admixture of division by powers of ten with division by powers of two that should never have seen the light of day.

A high capacity 90mm floppy disc that is low-level formatted in the standard manner has 2 sides, 80 tracks, and 18 sectors per track. There are thus 2880 sectors on the disc. Each sector holds 0.5KiB, which is 512 bytes, meaning that the formatted data capacity of the disc is 1440KiB, which is 1474560 bytes.

1474560 divided by 1024 squared is 1.40635. The formatted data capacity of a 90mm high capacity floppy disc in megabinarybytes is thus (approximately) 1.41MiB.

1474560 divided by 1000 squared is 1.47456. The formatted data capacity of a 90mm high capacity floppy disc in megabytes is thus (approximately) 1.47MB.

This is the data capacity of the entire disc after low-level format, of course. Some years after this Frequently Given Answer was first given, Microsoft published KnowledgeBase article 121839. That gives the data capacity of the files and directories after the filesystem metadata overhead of high-level formatting it with the FAT filesystem format is subtracted. One isn't required to format floppy discs with the FAT filesystem format, though, and the figure is different for other filesystem formats.


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